36 BRITISH FERNS. 



and become pinnate with obliquely fan-shaped three-lobed 

 pinnse ; and finally, the fertile fronds which are taller and 

 more erect in growth, are ovate, and two or three times pin- 

 nate ; the pinnse being alternate, ovate, with alternate pin- 

 nules ; the ultimate pinnules roundish, wedge-shaped, three- 

 lobed at the apex, the lobes rather distinct, and usually 

 notched at the end. The veins in each pinnule are branched, 

 so that one of the small veins proceeds towards each of the 

 teeth into which the pinnule is divided ; and the spore- 

 cases are borne along these branches of the veins. The lines 

 of sori on the pinnules often become united into a mass, 

 after they have been some time developed. 



Though a minute species, this fern is widely scattered 

 over the face of the globe ; it is plentiful in many parts of 

 the South of Europe, and extends as far northwards as 

 Jersey. 



It grows readily, as an annual, sown in sandy loam, and 

 kept in a rather warm damp situation. 



CHAPTEE VH 



THE SHIELD FERNS. 



THE Shield Ferns are called Polystichum. They form a 

 small and very distinct group of evergreen Ferns, some of 

 which rank among the most beautiful of our native species. 

 They once formed part of the genus Aspidium, in conse- 

 quence of their having round seed-patches covered by a scale ; 

 but that family, as far as the British kinds are concerned, is 

 Broken up by modern botanists, in whose ideas we coincide, 

 into two groups, called Polystichum and Lastrea. The Poly- 

 stichums are known from the allied Lastreas, by their having 

 the scale-like cover of the sori circular, without a lateral 

 notch, its attachment being by a little stalk in the centra 

 of the under side. This form of attachment is technically 

 called peltate. To a practised eye they are also known by 

 their more rigid texture, and by their haying altogether a 

 more spiny appearance than even the spinulose species of 

 Lastrea. Our alpine species, P. Lonc/iitis, is strictly ever- 

 green, and the other species acquire this character when in 

 a sheltered situation ; but if they are much exposed, the 

 fronds are killed by severe frosts. In general, however, they 

 all retain their fronds without much disfigurement from 



